Like many oceanographers, Julia Diaz is difficult to categorize. Is she a biologist, or is she a chemist? The answer is — a little of both. Diaz’s research interests lie where biology and chemistry meet.

“My absolute favorite thing in the world is looking at phytoplankton under the microscope,” she said. “And I am also very passionate about chemistry.

“Our chemical environment really shapes our health and impacts our climate and all kinds of natural resources. So I am interested in the intersection of those two parts of nature — how tiny microscopic life interacts with the invisible chemistry out there to shape the environment in some pretty big ways.”

Diaz joined the faculty of UGA Skidaway Institute of Oceanography in fall 2015 as a homecoming of sorts. She was raised in Alpharetta just outside Atlanta. She graduated summa cum laude from the University of Georgia with a degree in biology and then went on to earn a Ph.D. in earth and atmospheric sciences from Georgia Tech. Her postdoctoral work took her to Harvard University and Woods Hole Oceanographic Institution.

Diaz targeted science as her future from an early age. Her father is a retired Georgia State University professor, and her entire family was involved in education. Her brother is an astrophysicist, and she jokes that they study opposite ends of the universe—with her specializing in the very small while he studies the very large.

“I grew up talking about science with my dad, my brother and my mom,” she said. “It was always on my mind, and I was pretty good at it. It felt good to learn and to always be exploring new things.”

As an undergrad at UGA, her interest in science grew into a passion.

“I got into some really cool classes, where we basically spent two days out of the week staring down a microscope at pond water and it was just the coolest thing,” she said. “All these creatures that you would never imagine are there. It’s amazing — this whole other world that really drew me in.”

In graduate school, Diaz focused more on chemistry to complement her background in biology.

“I originally got interested in marine chemistry and biology because I was inspired by the fact that, billions of years ago, marine microbes created oxygen and other life-giving chemicals to make this planet the habitable place that it is,” she said.

Diaz’s work has taken her from the Caribbean to Antarctica.

“One of the best parts about this job is that it lets you see the world. Antarctica was the most amazing experience — you never get tired of seeing penguins,” she said.

Diaz with her penguin friends

“Personally, I never got tired of looking at Antarctic phytoplankton, either. They can attach to the underside of sea ice, making it look like it’s been dipped in coffee, but under the microscope, it’s like peering inside a jewelry box of gorgeous single cells, so many ornate shapes and vibrant colors. It’s just magical.”

Many of Diaz’s projects focus on phytoplankton — microscopic plantlike organisms that drift with the ocean’s currents. They form the base of the marine food chain and produce half of the oxygen in the atmosphere. Among other projects, she studies how starving phytoplankton obtain the chemical nutrients they need from seawater, and she attempts to identify the enzymes that drive those biogeochemical processes.

Diaz is also interested in how phytoplankton convert chemical elements into forms that can be harmful or beneficial to life, such as reactive oxygen species, or ROS, types of oxygen with additional electrons. They are produced in all living things as a byproduct of metabolism.

“ROS can be toxic, but they can also be very beneficial to life,” Diaz said. “They can serve as cell signals that promote growth and immune defense. Our own white blood cells produce ROS as a defense mechanism against invading pathogens.”

An important facet her work seeks to understand is how phytoplankton may use ROS to survive stressful situations, such as attack by predators. These ROS-driven processes may play a role in the formation and decline of giant phytoplankton blooms so large they can be seen by satellites.

She admits her work can be challenging to communicate outside of her field, because much of the research cannot be seen by the naked eye. However, she said, those invisible chemical processes are occurring in the ocean over sizeable areas and long time periods, and they produce large visible effects that shape our daily lives.

“From starvation to cell defense, a lot of the work I do relates to stress in the oceans — how marine life copes with stressful conditions, how stress changes the chemistry of the oceans and ultimately how that changes the environment on a global scale. The oceans are under increasing amounts of stress due to climate change, pollution and other human impacts, so I think this kind of research has an important place in the understanding of our changing planet.”